Sauce

1. Combine onion, garlic, tomatoes, arbol chiles and guajillo chiles in a medium saucepan and fill with water. Bring to a boil then reduce the heat to a simmer and cook until tomatoes start to split, about 15 minutes.
2. Remove from heat and let cool slightly.
3. Using a slotted spoon transfer the vegetables to a blender.
4. Add oregano, salt, cumin, allspice, pepper and vinegar.
5. Add 1 cup of the cooking liquid from the vegetables and blend on high until smooth.
6. Pour out remaining cooking liquid from the pan and pour the sauce back into the pan. Cover and keep warm over low heat.

Torta

1. Heat carnitas in the microwave or in a skillet until hot. Cover and keep warm.
2. Heat broiler to high.
3. Cut baguette in half lengthwise and spread beans on one half of the bread. Set on a baking sheet. Place the other half, cut side up, next to it on the baking sheet. Broil until beans are warm and bread is toasted, about 3 to 4 minutes.
4. Top the beans with the carnitas and onion.
5. Close sandwich with the other half of the bread. Set on a cutting board and cut into 4 sandwiches.
6. Set each torta in a shallow dish. Ladle sauce over each sandwich until it is completely covered with lots of sauce in the dish.

Garnish

1. Garnish with cotija cheese, and squeeze one or two lime wedges over the top.
2. Serve immediately with plenty of napkins.